In recent years many vectors and carriers have been developed for reliably delivering drugs, nucleic acids, peptides, proteins, sugar and the like to target sites. In the field of gene therapy, for example, retrovirus, adenovirus, adeno-associated virus and other virus vectors have been developed as vectors for introducing genes into target cells. However, because of such problems as difficulty of mass production, antigenicity, toxicity and the like associated with virus vectors, attention has shifted to liposome vectors and peptide carriers, which are less problematic. Liposome vectors offer the advantage of improved directionality towards a target site due to the introduction of an antibody, protein, sugar chain or other functional molecule on the surface of the liposome.
Liposome vectors that have been developed include for example a liposome vector that incorporates a complex of a polyarginine or other coagulant and a nucleic acid in capsule form (Japanese Patent Applications Laid-open No. 2002-520038). Peptide carriers that have been developed include a membrane-permeable Tat protein derived from HIV-1, polyarginine, an arginine-rich peptide and other peptide carriers (Japanese Patent Applications Laid-open Nos. 10-33186, 2001-199997).